The effect of social learning on the nocebo effect: a systematic review and meta-analysis with recommendations for the future

ABSTRACTIndividuals frequently update their beliefs and behaviours based on observation of others' experience. While often adaptive, social learning can contribute to the development of negative health expectations, leading to worsened health outcomes, a phenomenon known as the nocebo effect. This systematic review and meta-analysis examined: whether social learning is sufficient to induce the nocebo effect, how it compares to other forms of induction (classical conditioning and explicit instruction), and factors that influence these effects. The meta-analysis included twenty studies (n = 1388). Social learning showed a medium-large effect size (Hedges' g = .74) relative to no treatment and a to small-medium effect (g = .42) when compared to neutral modelling. The effect of social learning was similar in magnitude to classical conditioning but greater than explicit instruction with a small-medium effect (g = .46). Face-to-face social modelling, longer exposure, higher proportions of female participants and models, and greater observer empathy led to stronger socially-induced nocebo effects. However, further research is essential as only a minority of studies measured important constructs like negative expectancies and state anxiety. Nonetheless, the study highlights social learning as a key pathway for nocebo effects, suggesting it as a target for interventions to reduce the substantial personal and societal burden caused by nocebo effects.

Practitioner warmth and empathy attenuates the nocebo effect and enhances the placebo effect

Augmented patient-practitioner interactions that enhance therapeutic alliance can increase the placebo effect to sham treatment. Little is known, however, about the effect of these interactions on maladaptive health outcomes (i.e., the nocebo effect). Healthy participants (N = 84) were randomised to a 3-day course of Oxytocin nasal drops (actually, sham treatment) in conjunction with a high-warmth interaction (Oxy-HW: N = 28), a low-warmth interaction (Oxy-LW: N = 28) or to a no treatment control group (NT: N = 28). All participants were informed that the Oxytocin treatment could increase psychological well-being but was associated with several potential side effects. Treatment-related side effects, unwarned symptoms, and psychological well-being were measured at baseline and all post-treatment days. Side effect reporting was increased in the Oxy-LW condition compared to the other groups across all days. Conversely, increased psychological well-being was observed in the Oxy-HW condition, relative to the other conditions, but only on Day 1. Among those receiving treatment, positive and negative expectations, and treatment-related worry, did not vary by interaction-style, while psychological well-being and side effect reporting were inversely associated at the level of the individual. Results have important implications for practice, suggesting poorer quality interactions may not only reduce beneficial health outcomes but also exacerbate those that are maladaptive.

Learning by observing: a systematic exploration of modulatory factors and the impact of observationally induced placebo and nocebo effects on treatment outcomes

Introduction

Observational learning (OL) refers to learning through observing other people's behavior. OL has been suggested as an effective and simple tool to evoke treatment expectations and corresponding placebo and nocebo effects. However, the exact mechanisms by which OL shapes treatment outcomes, its moderating factors and possible areas of application remain unclear. We thus reviewed the existing literature with two different literature searches to answer the following questions: Which influencing factors contribute to OL-induced placebo and nocebo effects (in healthy volunteers and patients) and how large are these effects (search 1)? In which medical fields has OL been used so far to modulate treatment expectancy and treatment outcomes in patients, their caregivers, and at-risk groups (search 2)? We also aimed to explore whether and how the assessment of treatment expectations has been incorporated.

Methods

We conducted two independent and comprehensive systematic literature searches, both carried out on September 20, 2022.

Results

We identified 21 studies that investigated OL-mediated placebo and nocebo effects for pain and itch, the (placebo) efficacy of sham treatment on anxiety, and the (nocebo) induction of medication side effects (search 1). Studies showed that OL can efficiently induce placebo and nocebo effects across different presentation modes, with medium effect sizes on average: placebo effects, d = 0.79 (range: d = -0.36-1.58), nocebo effects, d = 0.61 (range: d = 0.04-1.5). Although several moderating factors have been investigated, their contribution to OL-induced effects remains unclear because of inconsistent results. Treatment expectation was assessed in only four studies. Regarding medical applications of OL (search 2), we found 12 studies. They showed that OL was effectively applied in preventive, therapeutic and rehabilitative interventions and that it was mainly used in the field of psychosomatics.

Discussion

OL effects on treatment outcomes can be both positive and negative. Future research should investigate which individuals would benefit most from OL and how OL can be implemented most effectively to induce placebo and avoid nocebo effects in clinical settings.

Systematic review registration

This work was preregistered at the Center for Open Science as open-ended registration (doi: 10.17605/OSF.IO/FVHKE). The protocol can be found here: https://archive.org/details/osf-registrations-fvhke-v1.

Socially Acquired Nocebo Effects Generalize but Are Not Attenuated by Choice

BACKGROUND

Socially observing a negative treatment-related experience has been shown to modulate our own experience with the same intervention, leading to worsened health outcomes. However, whether this social learning generalizes to similar but distinct interventions has not been explored nor what manipulations can reduce these effects.

PURPOSE

To determine whether socially acquired nocebo effects can be generated by observing a negative experience with a similar, but distinct intervention, and whether choice can reduce these effects.

METHODS

Across three experiments, a community sample of healthy adults (N = 336) either watched a confederate report cybersickness to the same Virtual Reality (VR) activity they were assigned to (Social Modeling: Consistent); a similar, but different VR activity (Social Modeling: Inconsistent); or did not view the confederate (No Social Modeling). Participants were either given choice over the VR (Choice) or assigned by the experimenter (No Choice).

RESULTS

Across the experiments, there was significantly greater cybersickness in both Social Modeling groups relative to No Social Modeling, while the two Social Modeling groups did not differ. There was no significant effect of Choice or a Choice by Social Modeling interaction. Social Modeling elicited greater anxiety and expectancies for cybersickness. Furthermore, these mechanisms mediated the association between social modeling and cybersickness.

CONCLUSIONS

Socially acquired side-effects were demonstrated to generalize to similar, but distinct interventions, highlighting the diffuse and robust effect social modeling can have on our experiences. However, choice did not attenuate the experience of cybersickness, highlighting the need for alternative methods to counteract the effect of social modeling.

Peer-to-peer: The Social Transmission of Symptoms Online

BACKGROUND

Social learning can be highly adaptive-for example, avoiding a hotplate your friend just burnt themselves on-but it has also been implicated in symptom transmission. Social learning is particularly pertinent given the rapid increase in the use of online mediums for social interaction. Yet, little is known about the social transmission of symptoms online or social chains extending further than a single model-observer interaction.

PURPOSE

To explore whether socially induced symptoms could be propagated through a three-generation social transmission chain in an online setting.

METHODS

We explored the social transmission of cybersickness following a virtual reality (VR) experience through online webcam interactions. One hundred and seventy-seven adults viewed a VR video in one of four links along a social transmission chain, after: viewing an actor model cybersickness to the VR video (First-Generation); viewing the First-Generation participant undergo VR (Second-Generation); viewing the Second-Generation participant undergo VR (Third-Generation); or naïve (Control).

RESULTS

Cybersickness was strongest in First-Generation participants, indicating social transmission from the model. This was mediated by expectancy and anxiety. Whether or not subsequent generations experienced cybersickness depended on what the observed participant verbally reported, which is consistent with social transmission.

CONCLUSIONS

Results demonstrate that symptoms can be readily transmitted online, and that expectancy and anxiety are involved. Although it is inconclusive as to whether symptoms can propagate along a social transmission chain, there is some evidence of protection from symptoms when a model who does not report any symptoms is observed. As such, this research highlights the role of social transmission in the modulation of symptoms through virtual mediums.

The influence of video-based social modelling on the nocebo effect

OBJECTIVE

Seeing someone else experience side effects (i.e., social modelling) can increase negative expectations and subsequent nocebo effects. In face-to-face contexts, this effect appears stronger in female participants. Less is known about the influence of gender on negative expectations and nocebo effects generated via video-based social modelling.

METHODS

One hundred and seven undergraduate participants recruited from a participant pool at an Australian university took part in a study ostensibly investigating the influence of beta-blocker medications (actually a sham treatment) on physiological and psychological aspects of anxiety. Participants were randomly assigned to either a no-treatment control group, a standard treatment group, or a video modelling group, in which participants viewed video-recorded confederates (one male, one female) report experiencing four side effects (two each) after taking the study treatment. Symptoms were assessed 15-min following pill ingestion, and at follow-up 24 h later.

RESULTS

Video modelling of side effects, compared to standard treatment, interacted with gender and was associated with increased reporting of modelled symptoms in female compared to male participants, p = .01, η_p²=0.06. Video modelling also increased negative expectations in female compared to male participants, p = .03, η_p²=0.07, and expectations mediated the influence of modelling on modelled symptoms in female participants.

CONCLUSIONS

Social modelling of side effects via video increased negative expectations, and nocebo symptoms, to a greater extent in female participants. These findings suggest that males and females are differentially impacted by video-based side effect modelling. Results have implications for social modelling of side effects via social media and patient-support websites.

Choice and the nocebo effect: If a little is good, more is better?

OBJECTIVE

Lack of choice over treatment may increase the nocebo effect, whereby unpleasant side effects can be triggered by the treatment context, beyond any inherent physiological effects of the treatment itself. Excessive choice may also increase the nocebo effect. The current studies tested these possibilities.

METHOD

Participants took part in studies ostensibly investigating the influence of beta-blockers (Study 1, n = 71) and benzodiazepines (Study 2, n = 120) on anxiety. All treatments were placebos. In Study 1, participants were randomly allocated to three groups: no-treatment control, no-choice, and choice between two treatments. In Study 2, a ten-choice group was added. Participants were warned about possible treatment side effects. These warned symptoms were assessed, and scores summed. Nocebo effects were evidenced by significantly higher warned symptoms scores in any placebo-treated group compared to the control group.

RESULTS

In both studies, the no-choice groups experienced a nocebo effect (S1: p = .003, η_p²= 0.121; S2: p = .022, η_p²= 0.045). A significant nocebo effect was not present in groups who chose between two treatments (S1: p = .424, η_p²= 0.009; S2: p = .49, η_p²= 0.004). In Study 2, choosing between ten treatments resulted in a nocebo effect (p = .006, η_p²= 0.065).

CONCLUSION

Lack of choice resulted in the development of nocebo effects, while having a limited choice between two placebos did not generate significant nocebo effects. However, a larger choice between ten placebos generated a nocebo effect of similar magnitude to lack of choice. Facilitating (some) choice in medical care may reduce the development of nocebo effects, but more extensive choice options may not offer similar benefits.

Psychosocial Factors Affecting Parental Report of Symptoms in Children: A Systematic Review

OBJECTIVE

Parents make important treatment decisions for their children based on symptoms they perceive their child to be experiencing. Multiple psychological factors are associated with subjective symptom perception, but factors affecting perception of symptoms in others have been explored less. We systematically reviewed the literature to identify parent and child psychological factors associated with parental report of physical symptoms in their child.

METHODS

We searched Embase, Ovid, PsycINFO, and Scopus for studies that investigated associations between psychological factors and parental report of symptoms in their child.

RESULTS

Thirty-six citations reporting on 34 studies that assessed the association between parent or child psychological factors and parental report of physical symptoms in the child were included in the review. Three main factors were identified as being associated with parental symptom report. First, there was evidence for an association between parental symptom report and affect, in particular parent and child anxiety. Second, child behavioral and conduct problems, and temperament-related challenges (problems with feeding and sleeping) were associated with parental symptom report. Third, parental expectations and beliefs that symptoms would occur were associated with parental symptom report, although few studies investigated these associations.

CONCLUSIONS

Parent and child affect, and parental expectations and beliefs may influence parents' cognition, causing them to pay more attention to their child, interpret their child's behavior as symptomatic, and recall symptoms in the child. Given the importance of parental perception of symptoms in driving decisions around care, additional research in this field is needed.

The Influence of Side Effect Information Framing on Nocebo Effects

BACKGROUND

One contributing factor to the development of nocebo effects is information provided about possible side effects. However, nondisclosure of information can be problematic.

PURPOSE

We assessed whether positively framed side effect information (highlighting likelihood of not experiencing side effects) can reduce nocebo effects compared to negatively framed information (highlighting likelihood of experiencing side effects).

METHODS

One hundred twelve participants took part in research ostensibly assessing the influence of benzodiazepines (actually sham capsules) on anxiety. Participants were randomized to receive a sham capsule with positively or negatively framed information about four side effects, or a no-treatment control condition. Side effect expectations were assessed after information provision. Framed side effects and other unmentioned symptoms were assessed during the session and 24-hr follow-up.

RESULTS

Nocebo effects occurred in symptoms presented as side effects (regardless of framing) during the study session and follow-up (ps < .003). At follow-up, there was also a nocebo effect in other unmentioned symptoms (p = .018). Positive framing reduced side effect symptoms compared with negative framing during the study session (p = .037), but this effect was no longer present at follow-up (p = .53). Side effect expectations did not differ between the framing conditions (p = .14).

CONCLUSIONS

Positive framing reduced side effects short-term, but not at follow-up. Expectations did not differ between negative and positive framing. Nocebo effects appeared to generalize to other unmentioned symptoms over a 24-hr period. Further research is needed to determine whether the initial impact of positive framing can be maintained over time.

Tripping on nothing: placebo psychedelics and contextual factors

RATIONALE

Is it possible to have a psychedelic experience from a placebo alone? Most psychedelic studies find few effects in the placebo control group, yet these effects may have been obscured by the study design, setting, or analysis decisions.

OBJECTIVE

We examined individual variation in placebo effects in a naturalistic environment resembling a typical psychedelic party.

METHODS

Thirty-three students completed a single-arm study ostensibly examining how a psychedelic drug affects creativity. The 4-h study took place in a group setting with music, paintings, coloured lights, and visual projections. Participants consumed a placebo that we described as a drug resembling psilocybin, which is found in psychedelic mushrooms. To boost expectations, confederates subtly acted out the stated effects of the drug and participants were led to believe that there was no placebo control group. The participants later completed the 5-Dimensional Altered States of Consciousness Rating Scale, which measures changes in conscious experience.

RESULTS

There was considerable individual variation in the placebo effects; many participants reported no changes while others showed effects with magnitudes typically associated with moderate or high doses of psilocybin. In addition, the majority (61%) of participants verbally reported some effect of the drug. Several stated that they saw the paintings on the walls "move" or "reshape" themselves, others felt "heavy… as if gravity [had] a stronger hold", and one had a "come down" before another "wave" hit her.

CONCLUSION

Understanding how context and expectations promote psychedelic-like effects, even without the drug, will help researchers to isolate drug effects and clinicians to maximise their therapeutic potential.

It is not just the drugs that matter: the nocebo effect

The role of psychological mechanisms in the treatment process cannot be underestimated, the well-known placebo effect unquestionably being a factor in treatment. However, there is also a dark side to the impact of mental processes on health/illness as exemplified by the nocebo effect. This phenomenon includes the emergence or exacerbation of negative symptoms associated with the therapy, but arising as a result of the patient's expectations, rather than being an actual complication of treatment. The exact biological mechanisms of this process are not known, but cholecystokinergic and dopaminergic systems, changes in the HPA axis, and the endogenous secretion of opioids are thought to be involved. The nocebo effect can affect a significant proportion of people undergoing treatment, including cancer patients, leading in some cases to the cessation of potentially effective therapy, because of adverse effects that are not actually part of the biological effect of treatment. In extreme cases, as a result of suggestions and expectations, a paradoxical effect, biologically opposite to the mechanism of the action of the drug, may occur. In addition, the nocebo effect may significantly interfere with the results of clinical trials, being the cause of a significant proportion of complications reported. Knowledge of the phenomenon is thus necessary in order to facilitate its minimalization and thus improve the quality of life of patients and the effectiveness of treatment.

Evidence of a Media-Induced Nocebo Response Following a Nationwide Antidepressant Drug Switch

In 2017, patients on a generic or branded antidepressant venlafaxine were switched to a new generic formulation (Enlafax). In February and April 2018, two major NZ media outlets ran stories about the new generic being less effective and causing specific side effects. This study aimed to examine the effect of the media coverage on drug side effects reported to the national Centre for Adverse Reactions Monitoring (CARM) and whether the specific symptoms reported in the media increased compared to side effects not reported in the media.

We analysed monthly adverse reaction reports for Enlafax to CARM from October 2017 to June 2018 and compared adverse reports, complaints of decreased therapeutic effect and specific symptom reports before and after the media coverage using an interrupted time series analysis.

We found the number of side effects and complaints of reduced therapeutic effect increased significantly following the media stories (interruption effect = 41.83, 95% CI [25.25, 58.41], p = .003; interruption effect = 15.49, 95% CI [7.01, 23.98], p = .012, respectively). The specific side effects mentioned in the media coverage, including suicidal thoughts, also increased significantly compared to other side effects not mentioned in the media.

In the context of a drug switch, media reports of side effects appear to cause a strong nocebo response by increasing both the overall rate of side effect reporting and an increase in the specific side effects mentioned in the media coverage, including reduced drug efficacy and heightened suicidal thoughts.

The study provides further evidence that media coverage of side effects can induce a nocebo effect.

This is the first study to look at media coverage of an antidepressant brand switch.

The increase in reported adverse events was higher for those symptoms mentioned in the media reports.

Can Positive Framing Reduce Nocebo Side Effects? Current Evidence and Recommendation for Future Research

Although critical for informed consent, side effect warnings can contribute directly to poorer patient outcomes because they often induce negative expectations that trigger nocebo side effects. Communication strategies that reduce the development of nocebo side effects whilst maintaining informed consent are therefore of considerable interest. We reviewed theoretical and empirical evidence for the use of framing strategies to achieve this. Framing refers to the way in which information about the likelihood or significance of side effects is presented (e.g., negative frame: 30% will experience headache vs. positive frame: 70% will not experience headache), with the rationale that positively framing such information could diminish nocebo side effects. Relatively few empirical studies (k = 6) have tested whether framing strategies can reduce nocebo side effects. Of these, four used attribute framing and two message framing. All but one of the studies found a significant framing effect on at least one aspect of side effects (e.g., experience, attribution, threat), suggesting that framing is a promising strategy for reducing nocebo effects. However, our review also revealed some important open questions regarding these types of framing effects, including, the best method of communicating side effects (written, oral, pictorial), optimal statistical presentation (e.g., frequencies vs. percentages), whether framing affects perceived absolute risk of side effects, and what psychological mechanisms underlie framing effects. Future research that addresses these open questions will be vital for understanding the circumstances in which framing are most likely to be effective.

Psychobiological Mechanisms of Placebo and Nocebo Effects: Pathways to Improve Treatments and Reduce Side Effects

Placebo effects constitute a major part of treatment success in medical interventions. The nocebo effect also has a major impact, as it accounts for a significant proportion of the reported side effects for many treatments. Historically, clinical trials have aimed to reduce placebo effects; however, currently, there is interest in optimizing placebo effects to improve existing treatments and in examining ways to minimize nocebo effects to improve clinical outcome. To achieve these aims, a better understanding of the psychological and neurobiological mechanisms of the placebo and nocebo response is required. This review discusses the impact of the placebo and nocebo response in health care. We also examine the mechanisms involved in the placebo and nocebo effects, including the central mechanism of expectations. Finally, we examine ways to enhance placebo effects and reduce the impact of the nocebo response in clinical practice and suggest areas for future research.